1. Field of the Invention
The present invention relates to an image recording device, especially relates to the image recording device in which a toner image is transferred and fixed on the paper.
2. Description of the Related Art
Conventionally, in an image recording device carrying out image exposure on a charged photoreceptor surface to form a toner image, the toner image is transferred on a transfer body such as paper or the like, and the image is fixed.
In the above mentioned image recording device, a toner is a charged powder, and the transfer body is charged by applying transfer voltage (transfer bias) having a polarity opposite to the toner, and the toner is transferred to the transfer body by electrostatically adsorbing the toner. However, especially in a case of a full color image, when plural kinds of toners are multiply transferred, a phenomenon in which the toners are scattered around the image (blur) often occurs. That is, toners transferred later around a toner image previously transferred are scattered, and then the scattered toners are observed as image blur. Even in the case of a monochrome image or single transfer, when a feeding speed of a transfer material becomes fast, a phenomenon in which toners are scattered around an image tends to be generated.
When the reason for blur is described with reference to an example using an intermediate transfer belt, two reasons can be considered, i.e., a reason such that in a transfer pre-nip section, a transfer electric field acts on an area in which a photo conductor and an intermediate transfer belt are not adhered, whereby the transfer electric field is bent toward a peripheral direction of the image by charge of toners previously transferred, and a reason such that after transferring a toner layer having predetermined charge to the intermediate transfer belt electrostatically and during when the toner layer is moved to a second transfer point, charge supplied from a primary transfer roller is damped from the intermediate transfer belt, whereby holding capability with respect to the toner is decreased so that the toner is scattered by a rebound of charges (of the same polarity) of the toner.
That is, as illustrated in FIG. 12A, when the toner 140 is transferred to the paper 122 which is fed in a white arrow direction, originally, the toner should be transferred as illustrated in FIG. 12B, however, as illustrated in FIG. 12C, the toner 140 flows backward in a feeding direction (the right side of FIG. 12C). Then a picture quality is deteriorated due to the toner 140 that has flowed backward on the paper 122 as the blur 141.
To restrict scattering (blur) of the toner such as described above, a transfer device having a conductive member in a space formed at an upstream side and/or a downstream side in an image carrying body moving direction near a transfer position and between an image carrying body and a rotating body for transfer is proposed (see for example, Japanese Patent Application Laid-Open (JP-A) No. 02-163779).
In the above-mentioned technique, scattering of the toner can be suppressed by applying voltage to a leading end portion of a transfer guide. However, there is a problem concerning the technique in that when voltage is applied to a chute member 14, in a case where resistance is lowered by water which is included in the paper, a transfer bias applied to a transfer section 18 escapes through the paper, resulting in a poor transfer (poor transferring effect).
Further, an image recording device which includes a sheet-shaped flexible member to which bias is applied before transfer and controls the voltage is suggested (see, for example JP-A No. 11-338276). However, in the device, bias is applied to prevent contamination of the transfer chute, and an effect of preventing toner from scattering is not mentioned.